<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        section{
            width: 80%;
            height: 150px;
            margin: 100px auto;
            display: flex;
        }
        section div{
            flex: 1;
            height: 100%;
            margin-right: 10px;

        }
        div:first-child{
            background-color:pink;
            flex: 2;
        }
        div:nth-child(2){
            background-color:purple;
        }
        div:nth-child(3){
            background-color:blue;
        }
    </style>
</head>

<body>
    <section>
        <div></div>
        <div></div>
        <div></div>
    </section>
</body>

</html>